After Silverlight 4.0 has been released with new WPF, I am kind of confused with these technologies: Silverlight? WPF? Windows Form?

The main motive that we want to achieve for BIG business project is following:

• Performance

• Security

• And platform independent**

If I consider all above three points then only Silverlight is the option as I don’t want people buying emulator on MacOS for WPF or Windows Form.

Now how good the Silverlight is for Business applications, I was completely against when Silverlight 2.0 was in the market but now it is Silverlight 4.0 and they have provided many new features (but still basics) that is required in any challenging business
applications.

Comparing Silverlight and WPF

-* Silverlight and WPF are very new technology and if I'd to compare from these two then I'd prefer WPF because it can be considered stable and mature. But it is not same as Windows Form.

-* If I go with Silverlight then I am sure about keep updating to the latest version of Silverlight. I remembered when we were developing software for version 2.0 then we'd to create our own framework with dynamic loading DLL, and then Navigation concept. But everything was got changed once Silverlight 3.0 came. I don't want this to be happening with this new product.

-* If we go with WPF then we don't get the platform independence.

Now, why not we just focus on making WPF and then move to Silverlght. As someone (Tim?) from Microsoft has said that the idea is to make Silverlight as close as WPF. But if that is the case then why XAML structure is different; I will not be convinced with by saying that .Net framework for SL is too small.. well the difference is coming from the namespace ?

I was searching on this subject and found "Microsoft WPF-Silverlight Comparison Whitepaper v1.1.pdf". This guide is very good that gives you ins-outs about how can we build common apps that runs on both. But again, it is comparing Silverlight 2 and not 4.

I am sure many architect/ developers/ project managers must be facing similar kind of questions in their premises and wants to initiate this discussion, if it has not been :).

We've still got 2 weeks to make this decision, so I'm expecting everyone to participate, gurus?